System and Method for Resource Allocation Device-to-Device for Open Discovery

ABSTRACT

A method for operating a mobile device adapted for device-to-device (D2D) communications includes determining a utilization measure for discovery resources (DRs) allocated for D2D discovery in a communications system, and sending a utilization measure report to an evolved NodeB (eNB) when a reporting criterion is satisfied, wherein the utilization measure report is configured to prompt an adjustment to a number of DRs allocated for D2D discovery when an adjustment condition is met.

This application claims the benefit of U.S. Provisional Application No.61/864,487, filed on Aug. 9, 2013, entitled “Estimating UE Density forDevice-to-Device (D2D) Resource Allocation,” which application is herebyincorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates generally to digital communications, andmore particularly to a system and method for resource allocationdevice-to-device (D2D) for open discovery.

BACKGROUND

Device-to-Device (D2D) technology is getting a lot of attraction becauseof the ability to offer new services, improve system throughput, and thelike. Next generation wireless communication protocols are likely toimplement D2D communication modes, where mobile stations communicatedirectly with one another rather than relaying wireless signals throughan intermediate cellular infrastructure, e.g., cell towers, and thelike. D2D communication may have a variety of practical advantageous,such as extending the coverage area of a cell or wireless local areanetwork.

SUMMARY OF THE DISCLOSURE

Example embodiments of the present disclosure which provide a system andmethod for resource allocation device-to-device (D2D) for opendiscovery.

In accordance with an example embodiment of the present disclosure, amethod for operating a mobile device adapted for device-to-device (D2D)operation is provided. The method includes determining, by the mobiledevice, a utilization measure for discovery resources (DRs) allocatedfor D2D discovery in a communications system, and sending, by the mobiledevice, a utilization measure report to an evolved NodeB (eNB) when areporting criterion is satisfied, wherein the utilization measure reportis configured to prompt an adjustment to a number of DRs allocated forD2D discovery when an adjustment condition is met.

In accordance with another example embodiment of the present disclosure,a method for operating an evolved NodeB (eNB) is provided. The methodincludes receiving, by the eNB, a utilization report from a mobiledevice, the utilization report corresponding to a utilization measurefor discovery resources (DRs) allocated for device-to-device (D2D)discovery in a communications system, and adjusting, by the eNB, anumber of DRs allocated for D2D discovery in accordance with theutilization report.

In accordance with another example embodiment of the present disclosure,a mobile device adapted for device-to-device (D2D) communications isprovided. The mobile device includes a processor, and a transmitteroperatively coupled to the transmitter. The processor determines autilization measure for discovery resources (DRs) allocated for D2Ddiscovery in a communications system. The processor sends a utilizationmeasure report to an evolved NodeB (eNB) when a reporting criterion issatisfied, where the utilization measure report is configured to promptan adjustment to a number of DRs allocated for D2D discovery when anadjustment condition is met.

In accordance with another example embodiment of the present disclosure,an evolved NodeB (eNB) is provided. The eNB includes a receiver, and aprocessor operatively coupled to the receiver. The receiver receives autilization report from a mobile device, the utilization reportcorresponding to a utilization measure for discovery resources (DRs)allocated for device-to-device (D2D) discovery in a communicationssystem. The processor adjusts a number of DRs allocated for D2Ddiscovery in accordance with the utilization report.

One advantage of an embodiment is that the number of resources allocatedfor D2D discovery is adjusted in accordance with utilization of theresources. Therefore, resources may be freed up for cellularcommunications in light use situations, while additional resources maybe allocated to support D2D discovery in heavy use situations.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure, and theadvantages thereof, reference is now made to the following descriptionstaken in conjunction with the accompanying drawing, in which:

FIG. 1 illustrates an example communications system according to exampleembodiments described herein;

FIG. 2 illustrates an example subframes supporting D2D open discoveryaccording to example embodiments described herein;

FIG. 3 illustrates an example plurality of subframes supporting D2D opendiscovery according to example embodiments described herein;

FIG. 4 illustrates an example subframe allocated for D2D open discoveryaccording to example embodiments described herein;

FIG. 5 illustrates an example subframe allocated for D2D open discovery,highlighting a discovery collision according to example embodimentsdescribed herein;

FIG. 6 illustrates a flow diagram of example operations occurring in aUE as the UE participates in a UE-triggered DR allocation processaccording to example embodiments described herein;

FIG. 7 a illustrates a flow diagram of example operations occurring inan eNB as the eNB participates in an eNB-triggered DR allocation processaccording to example embodiments described herein;

FIG. 7 b illustrates a flow diagram of example operations occurring in aUE as the UE participates in an eNB-triggered DR allocation processaccording to example embodiments described herein;

FIG. 8 illustrates an example first communications device according toexample embodiments described herein; and

FIG. 9 illustrates an example second communications device according toexample embodiments described herein.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The operating of the current example embodiments and the structurethereof are discussed in detail below. It should be appreciated,however, that the present disclosure provides many applicable inventiveconcepts that can be embodied in a wide variety of specific contexts.The specific embodiments discussed are merely illustrative of specificstructures of the disclosure and ways to operate the disclosure, and donot limit the scope of the disclosure.

One embodiment of the disclosure relates to resource allocationdevice-to-device (D2D) for open discovery. For example, a mobile devicedetermines a utilization measure for discovery resources (DRs) allocatedfor D2D discovery in a communications system, and sends a utilizationmeasure report to an evolved NodeB (eNB) when a reporting criterion issatisfied, wherein the utilization measure report is configured toprompt an adjustment to a number of DRs allocated for D2D discovery whenan adjustment condition is met.

The present disclosure will be described with respect to exampleembodiments in a specific context, namely communications systems thatsupport D2D communications and open discovery. The disclosure may beapplied to standards compliant communications systems, such as thosethat are compliant with Third Generation Partnership Project (3GPP),IEEE 802.11, and the like, technical standards, and non-standardscompliant communications systems, that support D2D communications andopen discovery.

FIG. 1 illustrates an example communications system 100. Communicationssystem 100 includes an evolved NodeB (eNB) 105 serving a plurality ofuser equipments (UEs), such as UE 110, UE 112, UE 114, and UE 116. eNB105 is serving the plurality of UEs by receiving transmission intendedfor a UE and then forwarding the transmitting to the UE or receiving atransmission from a UE and then forwarding the transmission to itsintended destination. In such a communications mode, eNB 105 and theplurality of UEs are said to be operating in a cellular mode. eNBs mayalso be commonly referred to as NodeBs, access points, base stations,controllers, communications controllers, and the like, while UEs mayalso be commonly referred to as mobile devices, mobiles, mobilestations, terminals, users, subscribers, stations, and the like.

D2D communications is a different operating mode where UEs can directlytransmit to one another without having their transmissions being relayedby an eNB. As shown in FIG. 1, UE 114 is communicating directly with UE120. UE 114 may be capable of communicating in the cellular mode, aswell as in the D2D mode. UE 120 is operating in a D2D mode, but it mayalso be possible that UE 120 is capable of operating in the cellularmode with eNB 105. However, such operation is not shown in FIG. 1.

While it is understood that communications systems may employ multipleeNBs capable of communicating with a number of UEs, only one eNB, and anumber of UEs are illustrated for simplicity.

In general, discovery is a process wherein a device can find otherdevices or be found by other devices. Through the discovery process, thedevice can find other devices with which to communicate. eNB assisteddiscovery is one form of discovery. In eNB assisted discovery, a UE isdirected to transmit a signal (e.g., a sounding reference signal (SRS)signal) and another UE listens and reports the signal quality to theeNB. The eNB may, based on the signal quality report, determine if D2Dcommunications (for example) can be enabled to the two UEs.

Open discovery is another form of discovery. In open discovery, UEsattempt to discover and be discovered by other UEs without being probed.Therefore, open discovery may be performed with limited facilitation byeNBs. According to an example embodiment, the eNB allocatescommunications system resources for the purpose of open discovery. Thecommunications system resources allocated for open discovery maygenerally consist of uplink (UL) subframes, however, othercommunications system resources may be used. With open discovery, any UEcan transmit a “beacon” signal, which may be referred to as a discoverysignal, in one or more allocated communications system resources toadvertise its presence to other UEs. In addition to transmittingdiscovery signals in communications system resources allocated fordiscovery, example embodiments disclose the use of discovery sequencesthat exploit time hopping to significantly improve the performance ofdiscovery. Example embodiments also disclose systems and methods todetermine communications system resources in which to transmit thediscovery signals.

Generally, D2D communication may occur over any network bandwidth. Insome example embodiments, D2D communication occurs on a UL portion ofthe network bandwidth in order to reduce the interference experienced bynearby UEs. More specifically, D2D transmissions on UL resourcesinterfere with the eNB. As long as the D2D UE is a reasonable distancefrom the eNB, the interference created by the D2D UE has little impacton the eNB. Conversely, on DL portions of the network bandwidth, D2Dtransmissions affect neighboring UEs, and potentially, their ability toreceive synchronization channels and physical downlink control channel(PDCCH) is affected, which may have a significantly higher negativeimpact than if the D2D UEs were transmitting on the UL.

FIG. 2 illustrates an example subframes 200 supporting D2D opendiscovery. Subframe 200 includes cellular subframes (such as subframes205 and 207) and D2D discovery subframes (such as D2D discovery subframe210 and 212). The D2D discovery subframes comprise a small percentage,such as 1%, of all subframes and are reserved for open discovery. Duringthe D2D discovery subframes, only discovery signals are transmitted andthere is usually no cellular communications.

FIG. 3 illustrates an example plurality of subframes 300 supporting D2Dopen discovery. Each subframe of subframes 300, such as subframe 305,includes a plurality of communications system resources, such asresource elements (REs). The entirety of a subframe may be allocated forD2D open discovery, such as subframes 307, 309, and 311. Subframesallocated for D2D open discovery may be periodic in nature. As anillustrative example, every N-th subframe may be allocated for D2D opendiscovery, where N is an integer value, such as 1, 2, 3, 4, 5, 6, 7, 8,9, and the like. It is noted that although the discussion focuses on theentirety of subframes being allocated for D2D open discovery, theexample embodiments discussed herein are operable with portions ofsubframes being allocated for D2D open discovery. Additionally, thediscussion mentions that that D2D open discovery subframes are periodicin nature. However, any subframe may be allocated for D2D open discoveryas long as the UEs know the location of the subframe so that they cantransmit discovery signals and listen for discovery signals of otherUEs.

FIG. 4 illustrates an example subframe 400 allocated for D2D opendiscovery. Subframe 400 includes a plurality of discovery resources(DR), such as DR1 405 and DR2 410. As shown in FIG. 4, subframe 400includes 6 DRs, however, other subframe configurations may havedifferent numbers of DRs. Each DR may comprise a set of REs within thesubframe. As an example, a DR may be an entire physical resource block(PRB) pair. As another example, a DR may be a subset of a PRB pair. Asyet another example, a DR may be multiple PRB pairs. As shown in FIG. 4,2 DRs of subframe 400 are occupied by discovery signals of UEs, with DR2415 being occupied by discovery signal A and DR5 420 being occupied bydiscovery signal B.

If there are not enough DRs allocated for the open discovery processwith respect to the number of UEs participating in the open discoveryprocess, the open discovery process will be inefficient. As an example,there will be a lot of collisions between discovery signals transmittedby the UEs, thereby resulting in many UEs not being discovered. On theother hand, if the number of DRs allocated is very large for the opendiscovery process with respect to the number of UEs participating in theopen discovery process, there will be a small number of collisions.However, many DRs will be unoccupied, resulting in excessivecommunications overhead and reduced communications capacity.

FIG. 5 illustrates an example subframe 500 allocated for D2D opendiscovery, highlighting a discovery collision. Subframe 500 illustratesa discovery signal collision in DR 505 with discovery signals DS A(e.g., transmitted by UE A) and DS C (e.g., transmitted by UE C). Thediscovery signal collision in DR 505 will likely result in other UEsbeing unable to detect neither of the two discovery signal andconsequently, neither of the two UEs. However, discovery signal DS B issuccessfully transmitted without collision in DR 510.

According to an example embodiment, UE-triggered and/or eNB-triggeredtechniques are provided to help an eNB adjust a number of resources(i.e., DRs) allocated for open discovery based on resource occupancy. Inother words, the eNB is able to adjust the number of DRs allocated foropen discovery based on a metric that measures utilization of the DRs.

According to an example embodiment, a UE is configured to trigger thereporting of metric values that measure utilization of DRs. The eNBtypically does not have to actively participate in UE-triggeredoperation. However, the eNB may be configured to provide the UE withinformation, such as thresholds, information about resources allocatedfor D2D discovery, and the like.

FIG. 6 illustrates a flow diagram of example operations 600 occurring ina UE as the UE participates in a UE-triggered DR allocation process.Operations 600 may be indicative of operations occurring in a UE, suchas UE 110, UE 112, UE 114, UE 116, UE 120, and the like, as the UEparticipated in a UE-triggered DR allocation process.

Operations 600 may begin with the UE determining a utilization measurefor a discovery subframe (blocks 605). The utilization measure mayprovide a representation of how many devices are transmitting in thediscovery subframe and therefore, the utilization of the discoverysubframe. The utilization measure may also provide a likelihood estimatefor a successful decoding of discovery signals transmitted in thediscovery subframe. As an illustrative example, a discovery subframewith a high utilization measure may have a large number of devicestransmitting in the discovery subframe, therefore a low likelihood thatdiscovery signals transmitted in the discovery subframe will besuccessfully decoded. Similarly, a discovery subframe with a lowutilization measure may have a small number of devices transmitting inthe discovery subframe, therefore a high likelihood that discoverysignals transmitted in the discovery subframe will be successfullydecoded.

An example implementation of the UE determining the utilization measurefor a discovery subframe (blocks 605) is as follows:

1. The UE may evaluate a metric for each DR in the discovery subframe(block 610). Evaluating the metric for a DR may result in a measuredvalue for the DR. The measured values may be numerical numbers that maybe representative of a number of devices (e.g., D2D devices, non-D2Ddevices, and the like) transmitting in the DRs of the discoverysubframe. The UE may be able to detect transmissions from devices ineach DR. As an example, one or more other D2D devices may betransmitting a discovery signal in a DR, while a non-D2D device may bemaking a transmission (uplink or downlink) in the DR.

As an illustrative example, the metric may be a signal to interferenceplus noise ratio (SINR) and the measured value is a SINR value. Ingeneral, a high SINR value for a DR may indicate that there arerelatively few devices transmitting in the DR. While a DR with a lowSINR value may indicate that there are relatively many devicestransmitting in the DR. The measured value, and potentially inconjunction with received energy or power, may allow the UE to determineinformation about the DRs. Another example metric may be success and/orfailure in discovery signal decoding. Table 1 illustrates occupationinformation about DRs as a function of SINR value (or similarly decodingsuccess and/or failure) and received energy (or power).

TABLE 1 DR occupation information as a function of SINR (or decodingsuccess and/or failure) and received energy (or power). SINR/successfuldecoding of discovery signal Low/Bad High/Good DR received LowUnoccupied DR Occupied by distant Energy or UE (no collision) Power HighOccupied by multiple Occupied by proximate UEs (collision) UE (possiblecollision)

As shown in Table 1, in a situation where the SINR value of a DR is high(or with successful decoding of a discovery signal) and the receivedenergy is low, the DR is likely to contain no transmissions ortransmissions from distant devices so no collision is expected. However,in a situation where the SINR value of a DR is high (or with successfuldecoding of a discovery signal) and the received energy is high, the DRis likely to contain transmissions from a proximate device andcollisions are possible. In another situation where the SINR value of aDR is low (or with unsuccessful decoding of a discovery signal) and thereceived energy is low, the DR is unlikely to be occupied so nocollision is expected. But, in a situation where the SINR value of a DRis low (or with unsuccessful decoding of a discovery signal) and thereceived energy is high, the DR does contain transmissions from multipledevices so collisions will most likely occur.

Although the discussion presented herein focuses on DRs in a discoverysubframe, the example embodiments are operable with otherconfigurations. As an example, the DRs may be part of a set of discoverysubframes, a radioframe, a fraction of a communications systembandwidth. Therefore, the discussion of DRs of a discovery subframeshould not be construed as being limiting to either the scope or thespirit of the example embodiments.

2. The UE may determine a number of DRs with measured values exceeding afirst threshold (block 615). According to an example embodiment, thefirst threshold may provide a representation of what is to be considereda high utilization of a DR. As an illustrative example, if the firstthreshold is set to a relatively small value, then DRs containingtransmissions from a small number of devices may be considered to behaving a high level of utilization, while if the threshold is set to arelatively large value, then only DRs containing transmissions from alarge number of devices may be considered to be having a high level ofutilization. The UE may simply compare the measured value from each DRin the discovery subframe against the first threshold and increment acounter whenever it finds a measured value that exceeds the firstthreshold.

3. The UE may determine an occupancy ratio for the discovery subframe(block 620). The occupancy ratio may be representative of the number ofDRs with measures exceeding the threshold to a total number of DRs inthe discovery subframe. In other words, the occupancy ratio may berepresentative of a fraction of DRs in the discovery subframe that havehigh utilization. The occupancy ratio may be the utilization measure.

The UE may report the utilization measure (occupancy ratio in theexample presented previously) to an eNB (block 630). The UE may reportthe utilization measure using a physical layer message. The UE mayreport the utilization measure using higher layer signaling. In general,the UE may report the utilization measure when a reporting criterion ismet. If the UE is to report the utilization measure without anyrestrictions, the reporting criterion may be always true. The UE mayreceive information about changes in the number of DRs allocated for D2Ddiscovery (block 635). Additionally, if the location of the DRs has alsochanged, the UE may receive information about the new location of theDRs.

However, to help reduce communications overhead, the UE may compare theutilization measure with a second threshold (block 625). If theutilization measure exceeds the second threshold, the UE will report theutilization measure to the eNB (block 630). If the utilization measuredoes not exceed the second threshold, the UE will not report theutilization measure. In such a situation, the reporting criterion may bethe utilization measure exceeding the second threshold. According toanother example embodiment, in order to help reduce communicationsoverhead, the UE may be configured to report an average of a pluralityof utilization measures, such as through the use of a sliding window ofdiscovery subframes. The size of the sliding window may be provided by atechnical standard, operator of the communications system, and the like.In such a situation, the reporting criterion may be that the UE hasgenerated an averaged utilization measure according to the slidingwindow. According to another example embodiment, in order to help reducecommunications overhead, the UE may be configured to report theutilization measure if there is sufficient change in consecutiveutilization measures. In such a situation, the reporting criterion maybe there being sufficient change in consecutive utilization measures.

According to an example embodiment, the first threshold and the secondthreshold may be specified in a technical standard, such as the 3GPP LTEstandards, broadcasted to the UE, sent to the UE in a system informationblock (SIB), sent by higher layer signaling, and the like. According toanother example embodiment, the first threshold and/or the secondthreshold may be consistent for all UE. The first threshold and/or thesecond threshold may differ for different UEs. As an illustrativeexample, some higher classes of UE with interference cancellingcapability may be able to detect a discovery signal at a lower SINRvalue than lower class UEs without the interference cancellingcapability. Consequently, such a UE may benefit from a lower firstthreshold.

According to another example embodiment, a situation where too many UEsare reporting utilization measures is avoided by having only a subset ofUEs be allowed to report. As an illustrative example, connected UEs, UEshaving a specified identification number substring, and the like, may beallowed to report. Alternatively, the eNB may specifically notify someUEs that they are allowed to report utilization measures. In such asituation, UEs not explicitly indicated that they are allowed to reportwould not send utilization measures.

According to another example embodiment, metrics other than occupationratio are used. Examples of other metrics include number of discoverysignals per discovery subframe, and the like.

According to an example embodiment, an eNB is configured to trigger thereporting of metric values that measure utilization of DRs. IneNB-triggered operation, both the eNB and the UE actively participate.

FIG. 7 a illustrates a flow diagram of example operations 700 occurringin an eNB as the eNB participates in an eNB-triggered DR allocationprocess. Operations 700 may be indicative of operations occurring in aneNB, such as eNB 105, as the eNB participates in an eNB-triggered DRallocation process.

Operations 700 may begin with the eNB sending a report request to the UE(block 705). According to an example, the report request may be a singlereport type request (i.e., an aperiodic request) where the eNB expectsthe UE to report the utilization measure after it receives the reportrequest. According to another example embodiment, the report request maybe a multiple report type request where the eNB specifies a reportperiod, a report time duration, and the like, for the UE. The eNB mayexpect the UE to report multiple utilization measures in accordance withthe report period, report time duration, and the like, specified in thereport request. According to yet another alternative embodiment, thereport period, the report time duration, and the like, may be specifiedby a technical standard or an operator of the communications system. Thereport request may be unicast to the UE on a physical layer controlchannel such as a common physical downlink control channel (PDCCH) or anenhanced PDCCH (EPDCCH), multicast if the report request is intended formore than one UE, or broadcast in specific message on a PDCCH or anEPDCCH. In a multicast or broadcast report request, the UEs may bespecified by UE type, radio network temporary identifier (RNTI) value,UE identifier, and the like).

According to an example embodiment, in order to help provide toleranceto transient type behavior, the report request specifies a slidingwindow size over which the UE is to average several utilizationmeasures. The report request message may also include thresholds, suchas the first threshold and/or the second threshold discussed previously.

The eNB may receive the utilization measure report from the UE (block707). The utilization measure report may be received as a physical layermessage or a higher layer message. According to an example embodiment,although the UE is expected to report the utilization measure (per thereport request), the UE may help to reduce communications overhead bynot reporting the utilization measure if it has not changed from apreviously reported utilization measure or if it has changed, but thechange is smaller than a specified threshold. In such a situation, theeNB may use the previously reported utilization measure until itreceives a newly reported utilization measure from the UE. The eNB mayadjust the allocation of the DRs if an adjustment condition is met(block 709). In other words, the eNB may adjust the allocation of theDRs in accordance with the utilization measure report. As anillustrative example, if the utilization measure report indicates thatthe DRs are being underutilized, the eNB may reduce the number of DRs.Similarly, if the utilization measure report indicates that the DRs arebeing over utilized, the eNB may increase the number of DRs. As anillustrative example, if the utilization measure indicates that the DRsare being underutilized even after the eNB has reduced the number ofDRs, the eNB may further reduce the number of DRs. As anotherillustrative example, if the utilization measure indicates that the DRsare being over utilized after a previously reported utilization measureindicating that the DRs are being underutilized (and the eNB reducingthe number of DRs), the eNB may elect to wait for another utilizationmeasure before adjusting the allocation of DRs to help prevent aping-pong condition from occurring by increasing the number of DRsimmediately after decreasing the number of DRs. The eNB may sendinformation about changes in the allocation of DRs to the UE (block711). Additionally, if the eNB changed location of the DRs allocated forD2D discovery, the eNB may send information about the location of theDRs to the UE.

FIG. 7 b illustrates a flow diagram of example operations 750 occurringin a UE as the UE participates in an eNB-triggered DR allocationprocess. Operations 750 may be indicative of operations occurring in aUE, such as UE 110, UE 112, UE 114, UE 116, UE 120, and the like, as theUE participated in an eNB-triggered DR allocation process.

Operations 750 may begin with the UE receiving a report request from theeNB (block 755). The report request may be a single report type request(i.e., an aperiodic request) specifying that the UE measure and report autilization measure for DRs. Alternatively, the report request may be amultiple report type request specifying a report period, a report timeduration, and the like, for the UE to measure and report multipleutilization measures for DRs.

The UE may determine a utilization measure for a discovery subframe(blocks 757). An example implementation of the UE determining theutilization measure for the discovery subframe may include the UEevaluating a metric for each DR in the discovery subframe (block 759),determining a number of DRs with measured values exceeding a firstthreshold (block 761), and determining an occupancy ratio for thediscovery subframe (block 763).

When a reporting criterion is met (e.g., receiving the report request,expiration of a reporting period timer, and the like), the UE may reportthe utilization measure to the eNB (block 765). The UE may receiveinformation about changes in the number of DRs allocated for D2Ddiscovery (block 767). Additionally, if the location of the DRs has alsochanged, the UE may receive information about the new location of theDRs.

According to an example embodiment, both UE-triggered reporting andeNB-triggered report are used. The UE-triggered reporting and theeNB-triggered reporting may use the same or different parameters, suchas thresholds, reporting UEs, and the like. As an illustrative example,eNB-triggered reporting may be used by specifying that UEs report at aspecified period and UE-triggered reporting may be employed to helpdetect unexpected changes in operating conditions. As an alternateillustrative example, eNB-triggered reporting may be used by specifyinga class or group of UEs to report at a specified period and UE-triggeredreporting may be employed to have any UE report changes in operatingcondition.

According to an example embodiment, both UE-triggered reporting andeNB-triggered report are used. The reporting parameters are sent to theUEs in a SIB message, with the same SIB message also indicatingdiscovery subframe configuration. The threshold may be set to be anumber of discovered D2D devices instead of SINR value. Furthermore, thereporting may be performed by all connected UEs. Generally, thereporting is aperiodic since the reporting does not need to be sent veryoften. If there are not a sufficient number of connected UEs, the eNBmay wake up some sleeping UEs. Furthermore, since UE distribution is notuniform but may include some hotspots (such as airports, train depots,shopping centers, and the like), the eNB may configure differentdiscovery subframes for different locations. UE-triggered reporting isusually employed when a UE experiences an unacceptable number ofdiscovery collisions.

FIG. 8 illustrates an example first communications device 800.Communications device 800 may be an implementation of a communicationscontroller, such as an eNB, a base station, a NodeB, a controller, andthe like. Communications device 800 may be used to implement variousones of the embodiments discussed herein. As shown in FIG. 8, atransmitter 805 is configured to transmit frames, report requests,discovery subframe information, and the like. Communications device 800also includes a receiver 810 that is configured to receive frames,utilization measure reports, and the like.

A report requesting unit 830 is configured to generate report requests.Report requesting unit 830 is configured to generate single report typerequests (i.e., an aperiodic request). Report requesting unit 830 isconfigured to generate multiple report type requests. Report processingunit 830 is configured to select UEs to receive the report requests.Report processing unit 830 is configured to specify parameters for thereports. A report processing unit 822 is configured to process receivedutilization measure reports. Report processing unit 822 is configured todetermine if an adjustment condition is met. A resource allocating unit824 is configured to allocate resources for D2D discovery. Resourceallocating unit 824 is configured to adjust an allocation of resourcesfor D2D discovery in accordance with the utilization measure reports. Amemory 830 is configured to store report requests, parameters for thereports, information about selected UEs, utilization measure reports,information about resources allocated for D2D discovery, thresholds, andthe like.

The elements of communications device 800 may be implemented as specifichardware logic blocks. In an alternative, the elements of communicationsdevice 800 may be implemented as software executing in a processor,controller, application specific integrated circuit, or so on. In yetanother alternative, the elements of communications device 800 may beimplemented as a combination of software and/or hardware.

As an example, receiver 810 and transmitter 805 may be implemented as aspecific hardware block, while report requesting unit 820, reportprocessing unit 822, and resource allocating unit 824 may be softwaremodules executing in a microprocessor (such as processor 815) or acustom circuit or a custom compiled logic array of a field programmablelogic array. Report requesting unit 820, report processing unit 822, andresource allocating unit 824 may be modules stored in memory 830.

FIG. 9 illustrates an example second communications device 900.Communications device 900 may be an implementation of a D2D device, suchas a UE, a user, a subscriber, a terminal, a mobile, a mobile station,and the like. Communications device 900 may be used to implement variousones of the embodiments discussed herein. As shown in FIG. 9, atransmitter 905 is configured to transmit frames, utilization measurereports, and the like. Communications device 900 also includes areceiver 910 that is configured to receive frames, report requests,discovery subframe information, and the like.

A request processing unit 920 is configured to process received reportrequests. Request processing unit 920 is configured to determine anature of the received report requests (e.g., single report typerequests or multiple report type requests) and configure communicationsdevice 900 accordingly. A metric processing unit 922 is configured toprocess measurements of signals in resources allocated for D2Ddiscovery, such as DRs in discovery subframes, to generate utilizationmeasures for the resources. A comparing unit 924 is configured tocompare values, such as measured values, utilization measures, and thelike, with thresholds. Comparing unit 924 is configured to determine ifthe values meet the thresholds. A report generating unit 926 isconfigured to generate reports in accordance with the utilizationmeasures and the report requests. Report generating unit 926 isconfigured to average multiple utilization measures and/or measuredvalues using a sliding window. Report generating unit 926 is configuredto determine if the utilization measures meet a difference thresholdused to help reduce communications overhead by reducing reports. Reportgenerating unit 926 is configured to generate report messages. A memory930 is configured to store report requests, parameters for the reports,utilization measures, measured values, utilization measure reports,information about resources allocated for D2D discovery, thresholds, andthe like.

The elements of communications device 900 may be implemented as specifichardware logic blocks. In an alternative, the elements of communicationsdevice 900 may be implemented as software executing in a processor,controller, application specific integrated circuit, or so on. In yetanother alternative, the elements of communications device 900 may beimplemented as a combination of software and/or hardware.

As an example, receiver 910 and transmitter 905 may be implemented as aspecific hardware block, while request processing unit 920, metricprocessing unit 922, comparing unit 924, and report generating unit 926may be software modules executing in a microprocessor (such as processor915) or a custom circuit or a custom compiled logic array of a fieldprogrammable logic array. Request processing unit 920, metric processingunit 922, comparing unit 924, and report generating unit 926 may bemodules stored in memory 930.

Although the present disclosure and its advantages have been describedin detail, it should be understood that various changes, substitutionsand alterations can be made herein without departing from the spirit andscope of the disclosure as defined by the appended claims.

What is claimed is:
 1. A method for operating a mobile device adaptedfor device-to-device (D2D) operation, the method comprising:determining, by the mobile device, a utilization measure for discoveryresources (DRs) allocated for D2D discovery in a communications system;and sending, by the mobile device, a utilization measure report to anevolved NodeB (eNB) when a reporting criterion is satisfied, wherein theutilization measure report is configured to prompt an adjustment to anumber of DRs allocated for D2D discovery when an adjustment conditionis met.
 2. The method of claim 1, wherein the DRs allocated for D2Ddiscovery form one of a discovery subframe, a plurality of discoverysubframes, a radioframe, and a subset of communications systembandwidth.
 3. The method of claim 1, wherein determining the utilizationmeasure comprises: determining a signal to interference plus noise ratio(SINR) value for each of the DRs allocated for D2D discovery;determining a number of DRs with SINR value meeting a SINR threshold;and deriving the utilization measure in accordance with the number ofDRs with SINR values meeting the SINR threshold and the number of DRsallocated for D2D discovery.
 4. The method of claim 3, wherein derivingthe utilization measure comprises dividing the number of DRs with SINRvalues meeting the SINR threshold by the number of DRs allocated for D2Ddiscovery.
 5. The method of claim 3, further comprising averaging theutilization measure with N previously derived utilization measures,where N is an integer value representing a size of a sliding window. 6.The method of claim 1, wherein determining the utilization measurecomprises: attempting to decode discovery signals in the DRs allocatedfor D2D discovery; determining a number of successfully decodeddiscovery signals; and deriving the utilization measure in accordancewith the number of successfully decoded discovery signals and the numberof DRs allocated for D2D discovery.
 7. The method of claim 1, whereindetermining the utilization measure comprises: determining one of anumber of DRs in the DRs allocated for D2D discovery with SINR valuesmeeting a SINR threshold and a number of successfully decoded discoverysignals in the DRs allocated for D2D discovery; determining one ofreceived energy levels and received power levels for the DRs allocatedfor discovery; and deriving the utilization measure in accordance withthe one of the number of DRs with SINR values meeting the SINR thresholdand the number of successfully decoded discovery signals and the one ofthe received energy levels and the received power levels.
 8. The methodof claim 1, wherein the reporting criterion is satisfied when theutilization measure exceeds a utilization threshold.
 9. The method ofclaim 8, wherein the utilization threshold is received from an evolvedNodeB (eNB).
 10. The method of claim 9, wherein the utilizationthreshold is received using radio resource control (RRC) signaling. 11.The method of claim 9, wherein the utilization threshold is received ina system information block (SIB).
 12. The method of claim 1, wherein thereporting criterion is satisfied when a reporting request is receivedfrom the eNB.
 13. The method of claim 1, wherein the reporting criterionis satisfied when a reporting period timer expires.
 14. The method ofclaim 1, wherein the reporting criterion is satisfied when a differencebetween the utilization measure and a previously reported utilizationmeasure exceeds a difference threshold.
 15. The method of claim 1,wherein the reporting criterion is satisfied when the utilizationmeasure is determined.
 16. A method for operating an evolved NodeB(eNB), the method comprising: receiving, by the eNB, a utilizationreport from a mobile device, the utilization report corresponding to autilization measure for discovery resources (DRs) allocated fordevice-to-device (D2D) discovery in a communications system; andadjusting, by the eNB, a number of DRs allocated for D2D discovery inaccordance with the utilization report.
 17. The method of claim 16,wherein the utilization measure is a ratio of a number of DRs allocatedfor D2D discovery with a signal to interference plus noise ratio (SINR)value exceeding a SINR threshold to the number of DRs allocated for D2Ddiscovery.
 18. The method of claim 16, wherein adjusting the number ofDRs allocated for D2D discovery comprises increasing the number of DRsallocated for D2D discovery when the utilization measure meets a firstthreshold.
 19. The method of claim 16, wherein adjusting the number ofDRs allocated for D2D discovery comprises decreasing the number of DRsallocated for D2D discovery when the utilization measure meets a secondthreshold.
 20. The method of claim 16, further comprising sending areport request to the mobile device.
 21. The method of claim 16, furthercomprising sending a message including a reporting period to the mobiledevice.
 22. A mobile device adapted for device-to-device (D2D)communications, the mobile device comprising: a processor configured todetermine a utilization measure for discovery resources (DRs) allocatedfor D2D discovery in a communications system; and a transmitteroperatively coupled to the transmitter, the processor configured to senda utilization measure report to an evolved NodeB (eNB) when a reportingcriterion is satisfied, wherein the utilization measure report isconfigured to prompt an adjustment to a number of DRs allocated for D2Ddiscovery when an adjustment condition is met.
 23. The mobile device ofclaim 22, wherein the processor is configured to determine a signal tointerference plus noise ratio (SINR) value for each of the DRs allocatedfor D2D discovery, to determine a number of DRs with SINR value meetinga SINR threshold, and to derive the utilization measure in accordancewith the number of DRs with SINR values meeting the SINR threshold andthe number of DRs allocated for D2D discovery.
 24. The mobile device ofclaim 23, wherein the processor is configured to divide the number ofDRs with SINR values meeting the SINR threshold by the number DRsallocated for D2D discovery.
 25. The mobile device of claim 22, whereinthe reporting criterion is satisfied when the utilization measureexceeds a utilization threshold.
 26. The mobile device of claim 22,wherein the reporting criterion is satisfied when a reporting request isreceived from the eNB.
 27. The mobile device of claim 22, wherein thereporting criterion is satisfied when a reporting period timer expires.28. The mobile device of claim 22, wherein the processor is configuredto attempt to decode discovery signals in the DRs allocated for D2Ddiscovery, to determine a number of successfully decoded discoverysignals, and to derive the utilization measure in accordance with thenumber of successfully decoded discovery signals and the number of DRsallocated for D2D discovery.
 29. The mobile device of claim 22, whereinthe processor is configured to determine one of a number of DRs in theDRs allocated for D2D discovery with SINR values meeting a SINRthreshold and a number of successfully decoded discovery signals in theDRs allocated for D2D discovery, to determine one of received energylevels and received power levels for the DRs allocated for discovery,and to derive the utilization measure in accordance with the one of thenumber of DRs with SINR values meeting the SINR threshold and the numberof successfully decoded discovery signals and the one of the receivedenergy levels and the received power levels.
 30. An evolved NodeB (eNB)comprises: a receiver configured to receive a utilization report from amobile device, the utilization report corresponding to a utilizationmeasure for discovery resources (DRs) allocated for device-to-device(D2D) discovery in a communications system; and a processor operativelycoupled to the receiver, the processor configured to adjust a number ofDRs allocated for D2D discovery in accordance with the utilizationreport.
 31. The eNB of claim 30, wherein the processor is configured toincrease the number of DRs allocated for D2D discovery when theutilization measure meets a first threshold.
 32. The eNB of claim 30,wherein the processor is configured to decrease the number of DRsallocated for D2D discovery when the utilization measure meets a secondthreshold.
 33. The eNB of claim 30, further comprising a transmitteroperatively coupled to the transmitter, the transmitter configured tosend a report request to the mobile device.